US 20060070948 A1
The invention described herein provides a novel modification of an aerobic bacterial generator, typically used for sewage wastewater treatment. By providing a pre-filter one creates the equivalent of a “sub-gravel filter” known to the aquarium trade. In such fashion the device is portable and can be placed at the bottom of any pond, lake or other body of water to act as an aeration and biological filtration device. Further the unit incorporates a means of inoculation and maintenance of cultures of beneficial bacteria within the device to improve digestion of organic residues as well as to compete with algae for mineral nutrients, thereby preventing noxious blooms of plant material.
1. A method of managing pond or fish culture facility water quality, the method comprising the steps of:
aerating and circulating the liquid in the pond or fish culture facility to facilitate the growth of facultative heterotrophic bacteria and autotrophic ammonia oxidizing bacteria added to the liquid in the form of an inoculum or allowed to develop naturally over the course of time.
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This application claims benefit of Provisional Patent Application No. 60/615,394, filed Oct. 4, 2004 and Provisional Patent application 60/709,906 filed Aug. 22, 2005.
1. Field of the Invention
The present invention relates to pond aerators and, in particular, to a type of aerator that enhances the growth of bacterial cultures beneficial to the maintenance of water quality in ponds or fish culture facilities.
2. Description of the Related Art
Ponds used for landscaping purposes or for the culture of aquatic plants or animals represent artificial environments that need to be managed in order to maintain water quality.
One of the most significant problems relating to water quality in such ponds is the buildup of mineral nutrients that stimulate the growth of plant materials such as algae. Such plants take advantage of these nutrients to foster the process of photosynthesis, through which the plants fix carbon from the atmosphere to form living cellular biomass.
As such living plant material accumulates, a byproduct of gaseous O2 is released, increasing the dissolved oxygen in the water during periods of illumination. However, during non-illuminated periods these same organisms must consume oxygen for normal aerobic metabolism.
A problem in the aquatic environment is that water has a limited ability to absorb and hold dissolved O2. Water at typical ambient temperatures is saturated with oxygen tensions ranging from only 7-10 mg/L. As algal cells accumulate, densities can be high enough to produce transient O2 tensions during active photosynthesis in excess of 20 mg/L.
These plants utilize oxygen for the various non-photosynthetic metabolic processes as they produce oxygen through photosynthesis. During sunlight the amount of oxygen produced is more than sufficient to meet the needs of their aerobic metabolism. However, any oxygen produced beyond a tension of 7-10 mg/L escapes into the atmosphere and therefore will not be available to the algae during periods of darkness when no more O2 is being released through photosynthesis.
Where nutrients stimulate the growth of sufficient biomass to require uptake of greater than the 7-10 mg/L available over the course of a nightly dark period, such plants can draw the dissolved oxygen concentration down effectively to zero. At such times aquatic animals, such as fish or crustaceans, being totally dependent on dissolved oxygen for survival, will die.
One means to deal with loss of dissolved O2 in ponds or fish culture facilities is to actively aerate the ponds. A wide variety of means of delivering air exist. One such means involves pumping of the water so that it is exposed to air such that it takes up oxygen in dissolved form. This can be done by spraying the water into the air or allowing it to flow over complex surfaces that mix the water or allowing it to splash back into the pond as a waterfall.
Another means is to send air directly into the water via air pumps or compressors. This air can be delivered through pipes or hoses as coarse bubbles or it can be delivered through diffusers such as air stones or membrane diffusers that reduce bubble size, thereby increasing the transfer of O2 to the water.
Another means of improving water quality beyond supplementing with O2 is to use either biological, mechanical or chemical means to remove plant material that cause the oxygen depletion in the first place. One way to do this is to pass the water through porous media, either within the pond or aquarium, or outside the system. Such filtration will strain algal cells from the water but will not typically remove dissolved nutrients. These nutrients will allow regrowth of algae and plants in the system.
Such filtration, however, can be enhanced by allowing the filter media to build up a colony of bacteria. These bacteria provide several benefits. They consume all forms of organic wastes in the pond, converting it to CO2 gas that can then escaped from the pond. They also compete with the algae for the mineral nutrients, preventing excess photosynthesis. They also can convert nutrients, especially nitrogenous compounds to less toxic forms, as well as to N2 gas, thus allowing excess nitrogen to dissipate from the liquid.
One common means of implementing media based biological treatment is through the use of a “sub sand” or “sub gravel” filter. This involves creation of a space beneath a porous “false” bottom consisting of sand, gravel or other granular material. A pump can then pump water out of that space with replacement water thereby being drawn slowly through the bottom granular medium such that it contacts the bacterial film that typically colonizes such medium.
One method of pumping water from a sub sand filter is through the use of an “air lift” pump. This consists of a tube that passes through the false bottom into the space below. An air hose is placed inside the tube and air is pumped and released as a bubble stream at the base of the tube. As the bubbles rise through the tube they expand in size as the pressure reduces with depth. This pushes water in front of the expanding bubbles and generates a current. As above, such water is replaced with water that diffuses slowly through the false bottom granular medium. Not only does such a device generate a water flow through the biological medium, it aerates the water as it does so.
The bacterial component of such systems can be allowed to develop in haphazard fashion through colonization with wild bacteria or it can be established using commercial strains as inoculants. One group of bacteria with beneficial properties is that of the “facultative bacteria”. These are predominantly aerobic species of bacteria but they also possess metabolic pathways that allow them to live in the absence of free O2.
Certain species in the group Bacillus are spore formers so they can readily be obtained as stable commercial cultures. Other groups such as Pseudomonas are not spore formers but can be stabilized as vegetative cells making them also commercially available.
A device is described in U.S. Pat. No. 6,780,318 that encourages growth of such facultative bacteria in wastewater treatment applications. It is commercially marketed as an ABG or Aerobic Bacterial Generator. This device uses the airlift principle described above to aerate and pass wastewater over a matrix within the column on which bacteria can grow. The device further describes a means through which commercial cultures of desirable bacteria can be introduced.
An advantage of this device is that it is scalable such that small versions can be used in small treatment vessels while larger, more powerful versions can be used in larger applications.
A second advantage is that the unit is portable. It can be incorporated as an integral component of a wastewater treatment vessel or it can be added as a completely transportable retrofit into any form of liquid vessel.
A specialized use of an ABG is described in Non-Provisional Patent Application #f10/984,009, filed on Nov. 8, 2004 for the purpose of carrying out the biological denitrification of nitrogenous compounds typically found in wastewater. Further a method to enhance this reaction is described in Provisional Patent Application No. 60/616,961 and Provisional Patent Application No. 60/709,906.
There exists a need to combine the above described processes such that a simple device can provide the benefits of aeration, mechanical filtration, biological media filtration and bacterial supplementation in a single, portable system that can be economically installed in ponds or other fish culture applications.
The present invention provides a method to treat water in a pond or fish culture facility so to improve clarity, preserve dissolved oxygen and prevent excessive blooms of noxious plant materials. The method includes the step of adding facultative bacteria to the pond or fish culture facility. The step of adding facultative bacteria includes the step of aerating and circulating the liquid in the pond or fish culture facility over a medium capable of supporting the growth of such bacteria.
The present invention also includes a method to enhance growth of a second group of bacteria that oxidizes ammonia compounds and acts in concert with the facultative bacteria to convert such oxidized nitrogen compounds to nitrogen gas so it can dissipate from the liquid.
The method also includes a means of delivering cultures of bacteria as well as specific nutrients to the system to supplement and control the bacterial colony existing in the system.
The present invention also includes an aerator and filtration device. The aerator/filtration device consists of a fine bubble diffuser at the base of a column which, when aerated, generates a water current through the column.
The column of the aerator/filtration device is filled with a matrix on which heterotrophic, facultative bacteria can attach and form a colony. Aerated water passing over this column exposes bacteria to nutrients and organic material contained in the pond or fish culture facility liquid.
The present invention also includes a method for introducing calcium carbonate material in the form of oyster shells, or other similar materials, within the column to act as a surface that stimulates growth and attachment of ammonia oxidizing autotrophic bacteria.
In the present invention the base of the column is surrounded and encompassed by a containment apparatus that acts as a pre-filter. This pre-filter contains a porous, fibrous matrix that mechanically filters incoming liquid and also supports the growth of attached facultative heterotrophic bacteria.
The method of the invention also includes a material consisting of calcium carbonate, in the form of crushed oyster shells or other similar materials, which stimulate colonization and growth of ammonia oxidizing bacteria in the external pre-filter.
In the present invention the diffuser within the aerator/filtration device is supplied with air from a remote air pump or compressor delivered through a pipe or hose connected from the pump to the diffuser.
The method also includes a hose passing from the surface down and into the pre-filter matrix portion of the device through which liquid cultures of facultative heterotrophic bacteria and/or ammonia oxidizing bacteria can be added as needed.
The method also provides a central tube within the column of the device that allows a porous packet of bacterial cultures to be added and held within the aerated water column generated by the airlift action.
The liquid in the pond or fish culture facility contains nutrients that stimulate blooms of photosynthetic algae that can degrade water quality and depress the level of dissolved oxygen.
The facultative bacteria added to the pond or fish culture facility compete for nutrients and supplant the algal community and prevent the deterioration of water quality due to excessive photosynthetic loading to the pond or fish culture facility while the ammonia oxidizing bacteria can initiate conversion of ammonia to nitrogen gas in concert with the facultative heterotrophic bacteria.
Following this, method 200 moves to step 212 to add facultative bacteria such that the growth of the facultative bacteria is enhanced by the aeration and circulation of the liquid in the pond or fish culture facility. As a result of the aeration and circulation of the liquid the added bacteria will flourish and colonize surfaces within the pond or fish culture facility, thereby enhancing the bacteria's ability to digest organic and mineral nutrients within the liquid.
Following this, method 300 moves to step 312 to add ammonia-oxidizing bacteria to the pond or fish culture facility. The ammonia oxidizing bacteria convert ammonia to nitrite and the facultative heterotrophic bacteria convert nitrite to gaseous nitrogen, which can dissipate from the liquid to the atmosphere.
The host material for the facultative heterotrophic bacteria provides a surface for the bacteria to grow on that increases the number of facultative heterotrophic bacteria that are present in the pond or fish culture facility. In the preferred embodiment, the bacterial host material is placed adjacent to the aeration source so that the bacterial host material is bathed in air and waste material when the aeration source is in operation.
The host material for the ammonia oxidizing bacteria provides a surface for the bacteria to grow on that increases the number of ammonia oxidizing bacteria that are present in the pond or fish culture facility. In the preferred embodiment, the bacterial host material is placed adjacent to the aeration source so that the bacterial host material is bathed in air and waste material when the aeration source is in operation.
Further the host material for the ammonia oxidizing bacteria is placed adjacent to the host material for the facultative heterotrophic host material so that as ammonia is oxidized by the ammonia oxidizing bacteria to nitrite, the nitrite is readily available to the facultative heterotrophic bacteria so that they can convert the nitrite to nitrogen gas. In such fashion the nitrogen can readily dissipate from the liquid.
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Aerator/filtration device 600 also includes a compressed air line 616 that is connected to the air input side of air diffuser 610, and an air compressor (or blower) 618 that is connected to the compressed air line 616. Compressor 618, which is located a distance away from diffuser 610, can be implemented with, for example an 80-watt compressed air pump. Line 616 provides diffuser 610 with pressurized air pumped from compressor 618.
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Aerator/filtration device 600 optionally includes a bacterial host material 620 that is positioned within the column 614 that extends away from diffuser 610. Material 720 is positioned a predetermined distance away from the bubble output side of the diffuser 610, measured normal to the surface of the bubble output side. Material 620 can be any material that provides a surface area for bacteria to grow and that water can pass through without clogging.
Material 620 is preferably manufactured from a material that is resistant to decay, and configured and placed within the column in a fashion that provides the maximum possible film forming surface area with the volume of the column. Material 620 is placed to allow for the free flow of both liquid and air through material 620. For example, material 620 can be implemented with a sheet of cuspated plastic material manufactured similar to the method described in U.S. Pat. No. 4,449,072, which is hereby incorporated by reference.
Aerator/filtration device 600 additionally includes a bacteria container/applicator 622 that is positioned within column 614 that extends away from diffuser 610. Container 622 is positioned a predetermined distance away from the bubble output side of diffuser 610, measured normal to the surface of the bubble output side. Bacteria container/applicator 622 includes a porous sack, or any other similar packaging, which can contain a bacterial starter culture allowing timed release of viable bacteria over a prolonged period or the outlet end of a tube or other means to deliver bacteria from an external source.
To maintain the position of bacterial host material 620 and bacterial container/applicator 622 within the column that extends away from diffuser 610, material 620 and container/applicator 622 can be connected to airline 616. Alternately, device 600 can include a frame or structure to provide the necessary positional relationships.
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Pre-filter 724 is a closed unit that is perforated with openings 728 to allow liquid to enter into the device through the majority of the filter material 726 as it passes into the zone of the air diffuser 610 and into the column 614 which extends away from diffuser 610 and over the material 620 within the column that acts as a matrix for bacterial settlement and past container 622 that contains a bacterial culture.
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